As mobile phones, digital AV devices, IC cards and the like are highly functionalized, it is more demanded that a semiconductor silicon chip (hereafter referred to as “chip”) be highly integrated in a package by making a mounted chip smaller and thinner. For instance, there is a demand for thinning an integrated circuit obtained by packaging a plurality of chips, such as CSP (chip size package) and MCP (multi-chip package). In order to fulfill high integration of a chip in a package, it is necessary to thin a chip down to a range of 25 μm to 150 μm.
However, a semiconductor wafer (hereafter referred to as “wafer”) serving as a base of a chip becomes thin by grinding. Therefore, strength of the wafer decreases. This is likely to result in a crack or a warpage in the wafer. Furthermore, it is difficult to automatically carry the wafer whose strength decreases due to its smaller thickness. Therefore, it is necessary to manually carry the wafer and it is troublesome to handle the wafer.
For this reason, there has been developed a wafer handling system for reinforcement of a wafer, by which to adhere a plate called “supporting plate” which is composed of glass, hard plastic or the like, to a wafer to be ground, thereby preventing a crack and a warpage in the wafer. Since the wafer handling system can reinforce a wafer, it is possible to automatically carry a wafer having been made thinner.
In the wafer handling system, (i) a wafer and a supporting plate are adhered together with the use of various kinds of thermoplastic resins or adhesives, (ii) the wafer adhered to the supporting plate is thinned, and then (iii) the supporting plate is stripped from the wafer prior to dicing of the wafer. In order to thin the wafer to 150 μm or less, for example, it is highly preferable to firmly adhere the wafer and the supporting plate together.